Sidibe appears in the final season of Showtime's "The Big C," which premieres Monday. She made a splash in the gritty film, "Precious," in 2009 and went on to win an Oscar for the role. Her film credits include "Tower Heist" and "Seven Psychopaths."

As one could assume from the "American Horror Story: Coven" title, the third installment will focus on witches. "It's a really cool story that we've been talking for a couple years, and this seemed to be the year to do it," Murphy said in March at PaleyFest.